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INFA640Homework2Summer2020A.docxINFA 640 Homework 2
The questions 1 thru 5 weigh 5 pts each. The sixth Question carries 25 pts. pg. 1
Choose the best answer (one) and give reason in a few sentences for your choice or not choosing others. Please give a reference. To get full credit the reason should be in your own words, not a copy from any reference. Without reason in your own words you will not get full credit. Please name your file as [Last name First_ name INFA640_ HW2] Due last day of the session 9 Tuesday 11:59 PM
1) Claude Shannon presented the encryption design principles of _________________.
a) diffusion and confusion
b) multiplication and factoring
c) exponentiation and Logarithms
d) perplexion and reflection
Reason: how and why those principles guide the encryption?
2) To create a digital signature, a sender needs the plain text, the asymmetrical encryption algorithm, and ___________.
a) his/her public key
b) the receiver’s public key
c) his/her private key
d) the receiver’s private key
Reason How is it used?
3) A good hash function creates _________ mapping between the source string and the output string.
a) complex
b) as many as needed
c) divisional
d) one to one
Reason why is it considered good?
4) Repudiation means
a) Faking one’s identity
b) Uproot
c) Deny ownership
d) Plant clues in the text
Reason: Why it is important?
5) A number is relatively prime to another if they _____________.
a) have only each other as factors
b) have no prime factors in common
c) only have one prime factor in common
d) are both divisible by 7
Reason:
?
6) (25 pts) The following is a ciphertext:
O YOFR MIT UKTAM MIOFU OF MIOL CGKSR OL FGM LG DWEI CITKT CT LMAFR, AL OF CIAM ROKTEMOGF CT AKT DGXOFU: MG KTAEI MIT HGKM GY ITAXTF, CT DWLM LAOS LGDTMODTL COMI MIT COFR AFR LGDTMODTL AUAOFLM OM - ZWM CT DWLM LAOS, AFR FGM RKOYM, FGK SOT AM AFEIGK. DAFB ORTAL UKGC ZTMMTK CITF MKAFLHSAFMTR OFMG AFGMITK DOFR MIAF OF MIT GFT CITKT MITB LHKAFU WH.
GSOXTK CTFRTSS IGSDTL, LK
a) What kind of cipher text is this? Mono- or Poly alphabetic; {Hint: assume one and when that does not work look for the other} {2 points}
b) Describe your cryptanalysis process. List all the steps, every one of them you went through to decrypt the message. The steps should be in sufficient details so that a reader would be able to decrypt the encrypted text without needing any help from you.
If you find solution online or use online tools please give reference. However, you should describe the steps as if you are working without the tool, (Hint consider starting with the frequency analysis) to get full credit. If you list partial steps you will get partial credit
{18 points}
c) State the plain text message in readable form i.e. separating words if required. {2 pts}
d) List features of the cipher- text that hindered and helped your decryption process. mention of helpful and hindering features {3 pts}
Note: Only a decrypted message even if it is correct one without the methodology and the detailed description of the self-explanatory steps used to decrypt, would not get points.
